Optical instrument illumination control



OPTICAL INSTRUMENT ILLUMINATION CONTROL Filed May 4, 194e j 2 sheets-sneet'z f 7L ATTORNEYS Patented July 19, 1949 OPTICAL INSTRUMENT ILLUMINATION CONTROL Clarence W. Wallhausen, Morristown, N. J., as-

signer to United States Radium Corporation, New York, N. Y., a corporation of Delaware Application May 4, 1946, Serial No. 667,436

9 Claims.

This invention relates to the illumination of optical instruments and especially to the lighting of reticles.

In brief, the invention comprises the illumination of reticles or the like by the glow produced by an area of non-radioactive luminescent phosphor, the activation of which is effected by an roverlapping area of suitable non-luminescent radioactive material located adjacent thereto, means being provided for changing the amount of' activating radiations which impinge on the phosphor, preferably so as to adjust the intensity of illumination from zero to maximum.

Many types of optical instruments such as telescopes, range finders, transits and periscopes, include a reticle (or reticule) which may comprise, for example, a glass disc having two plane surfaces on one of which are engraved cross hairs or calibration marks. In using the instrument, it is necessary to see the marks or indicia (hereinafter called cross hairs) under widely differing light conditions. For instance, a range nder or a periscope for modern use must be employed in brilliant daylight when subject to considerable reflection from the water, at night in substantially total darkness, and in all degrees of intermediate light conditions. Under some of these conditions the cross hairs are satisfactorily visible Without artificial illumination, but under other conditions, notably during twilight, the cross hairs are very difficult or impossible to see.

To alleviate these disadvantages, three principal proposals have been made. First, the reticle has been edge-lighted by small electric lamps, second, the cross hairs or indicia themselves have comprised a phosphorescent substance which would glow When activated by an ultra-violet lamp placed at one side of the reticle, and, third, the reticle has been edge-lighted by coating the periphery thereof with self-luminous paint.

All of these proposals, while tosome extent effective in causing the cross hairs to be visible, have introduced new disadvantages which have made them impracticable for many purposes.

The first and second proposals include electric lamps, batteries or other sources of power, and electric Wiring and controls. Especially in small optical instruments, such additional equipment cannot be accommodated, and furthermore, it adds many extra components subject to breakdown, in addition to the difficult requirement for reliable electric power. The third proposal, which comprises coating the periphery of the reticle with a self-luminous paint, is in several respects an improvement over the first two proposals, but

this arrangement provides a continuous non-adjustable illumination which is especially troublesome under twilight conditions which require a close adjustment of the degree of illumination to afford satisfactory operation. However, the more serious disadvantage results from the fact that self-luminous paints, which comprise a phosphor activated with a radioactive material ntermixed therewith, must be caused to glow at a high intensity in order to provide suihcient light. To achieve this high degree of luminosity the phosphor must be activated at such a high rate that its useful life is very short. In most cases such life would not be more than one month, and in many cases not more than two Weeks, after which a new reticle with a fresh coating must be substituted in the instrument, or the old reticle removed and a new coating applied to it. Neither of these practices is feasible in connection with marine or other remote uses, because in the first case the spare reticles would deteriorate at the same rate as those in use, and the second case calls for laboratory techniques which are not ordinarily available at sea or other remote locations.

In accordance with the present invention, the edge or periphery of the reticle is coated with a luminescent but a non-radioactive phosphor, or preferably such phosphor is applied to a thin, translucent, plastic strip, or a ring, which may readily be applied to, or fitted around, the periphery of the reticle so as to permit of easy replacement. The radioactive material is, in accordance with my invention, not admixed with the phosphor, but comprises a separate element having an area which is positioned closely adjacent that of the phosphor, so that the radiations from this material may impinge on and activate the phosphor.

In accordance With a preferred form of the invention the radioactive material is arranged to be movable with respect to the phosphor coating on the reticle so that the respective areas may be adjusted to overlap completely giving maximum illumination, or so as not to overlap at all giving zero illumination, or so as to overlap to any desired intermediate degree to provide a correspending adjustment of the intensity of illumination. Thus the active life of the phosphor is greatly increased because the phosphor deteriorates only during actual use, Viz., while being subn jected to bombardment by activating radiations. This feature of my invention is more generally described and claimed in my copending application for U. S. Letters Patent Serial No. 658,379, led May 9, 1946.

A better understanding of the invention may be had from the following description considered together with the drawings, of which:

Fig. 1 illustrates the `eye-piece of an optical instrument, such as a telescope, the portions pertinent to the present invention being shown in vertical cross-section;

Fig. 2 represents a cross-sectional view along the line 2-2 of Fig. l looking in the direction of the arrows;

Fig. 3 is a cross-sectional view taken along the line 3-3 of Fig. 1, looking in the direction of the arrows, the illuminating members being in the positions providing minimum illumination;

Fig. 4 is a cross-sectional View similar to that of Fig. 3, but differing therefrom in that the illuminating members are shown in the positions providing maximum illumination;

Fig. 5 illustrates an eye-piece, generally similar to that of Fig. 1, but in which the adjustable features comprise an alternative embodiment;

Fig. 6 is a vertical cross-sectional view taken along the line 6-6 of Fig. 5, looking in the direction of the arrows; and

Fig. "I is a fragmentary view corresponding to a portion of Fig. 5, but with the movable elements adjusted to provide minimum illumination, whereas Fig. 5 illustrates the same elements in position to provide maximum illumination.

Figs. 1, 2 and 3 show an eye-piece tube I in which a glass reticle 2 is concentrically mounted by a gripping ring 6. This ring is held in place on the inside of the tube I by a threaded inner retaining ring 4' against which the spring ring 6 is pressed by a threaded outer retaining ring 5. The reticle 2 carries cross hairs 3, or additional indicia marks 3a (Fig. v2) which it is desired to illuminate.

Around the periphery of reticle 2 is fitted a thin strip or ring 9a of translucent material, such as a suitable plastic, which is coated cn the er.- terior surface with a non-radioactive luminescent phosphor material 9. If this strip is in the form of a closed ring and the inside diameter thereof is such as to fit snugly around the periphery of the reticle it may be slid on the same and retained there by normal friction. Alternatively, the coating may be Aapplied to a flat or curved strip of suitable material which may be secured around the periphery of the reticle by any appropriate means, such as cement. The prosphor may also be painted on, or otherwise applied directly to the edge or periphery of the reticle, but as above pointed out this operation ordinarily requires laboratory techniques and does not so readily permit renewal of the phosphor under "field or other difficult conditions.

Various luminous phosphor materials are suitable for the purposes herein described and it is usually desirable to select a phosphor which is best adapted to the conditions under which the particular instrument is to be used. For eX- ample, a phosphor comprising Zinc sulphide provides a yellowish green light which is desirable under many circumstances because of its high brilliancy, and on the other hand a phosphor comprising cadmium silicate provides a less brilliant and orange light which is sometimes desirable. A phosphor comprising cadmium'tungstate provides a pale bluev light. Suitable mixn tures of these or other phosphors are sometimes useful. The area or areas of phosphor should be applied in a thin coating so that the luminous particles thereof will not be masked by other particles. A more complete discussion of suitable phosphors and means for using them is given in my mentioned application Ser. No. 668,379. It will now be apparent that the present invention permits of several such coated strips or rings being kept on hand so that the desired one may be selected and employed under any given conditions.

From the discussion above it will be recalled that the radioactive material is, in accordance with my invention, mounted separately from the phosphor, in order (1) to increase the life of the phosphor by subjecting it to activating radiations only when illumination is required, and (2) to provide adjustability of the intensity of illumination. Hence, in accordance with the invention, a suitable radioactive material I0 is arlixed to a rotating ring having an inner section 3 and an outer section l, the radioactive material being suitably secured to the inner section 8. The in ner and outer sections are fastened together at three equi-distant points where the inner ring carries a post portion I5 which extends through a suitable slot in the tube I. There being three such post portions, three corresponding slots I6 in the tube I are required.

As shown more clearly in Figs. 2, 3 and 4, the periphery of the reticle 2 is coated with three phosphor areas 9 equidistantly spaced therearound. Three corresponding areas of radioactive material I0 are provided on the inside surface of the inner ring section 8. Of course, as many coacting areas as desired may be employed. When the ring 1, 8 is turned so that the areas 9 and IU do not overlap, as shown in Figs. 2 and 3, substantially no activating radia tions from radioactive surfaces I0 will impinge upon the surfaces of the phosphor areas 9, with the result that the phosphor areas 9 will not glow and hence their active life will be maintained inn definitely. On the other hand, when the ring is turned to the right (in Fig. 3, in the4 direction of the arrow labeled Illuminate") the areas 9 and Iii will be caused to overlap progressively until they overlap completely as shown in Fig. 4. In this manner the intensity of illumination can be adjusted from substantially zero to maximum. The mechanism should preferably be constructed to provide very close spacing between the areas 9 and I9 when in the position of Fig. 4.

Although in accordance with the invention any radioactive material suitable to activate a desired phosphor may be employed for the purpose, I prefer to utilize radioactive foil of the types described in U. S. Patent No. 2,326,631 to Fischer, and in my joint application for U. S. Letters Patent Ser. No. 654,460, filed March 14, 1946. The useful life of such radioactive foil is longer than the expected life of the instrument.

The rotating ring 1, 8 may be arranged as above described for manual movement in either direction, there being suilicient friction between the ring members I and 8 and the tube l to hold the ring in any desired position. However, in some types of optical instruments, it is expedient to attach one or more springs to the rotating ring so that when the ring, is manually moved toward the position shown in Fig. 4 it will, when released, be automatically returned by the action of the springs to the position shown in Fig. 3. For this purpose two springs II (Figs. 1 and 2) may be positioned along the two edges. of the. outer section 1 of the rotating ring against the outside of tube I. Oney end of each springv is attached to the ring 'i andthe other end vis attached to the tube l, so that when the ring section 'l is manually rotated the springvis stretched. Upon manual release o the ring section 1, the springs will automatically rotate the ring to the position shown in Fig. 3.

The alternative form of the invention disclosed in Figs. 5, 6 and 7 provides substantially the same results as those obtained from the embodiment above described, but employs a different mechanical arrangement. In illustrating the present embodiment the components which correspond functionally to those shown in Figs. l-4, inclusive, have been given the same reference numbers, plus lii. This embodiment will, therefore, be described chiefly for the purpose of pointing out the features wherein it differs from the embodiment first described.

In Fig. the reticle |02 carries a coating it?) of phosphor applied to a strip or band [59a ci translucent material, as before described. In this case, however, it is feasible to employ a conl tinuous band of phosphor ,|09 around the periphery of the reticle, as shown more clearly in Fig. 6.

Instead of .being supported on a rotating ring the radioactive material lil is in this embodiment supported on a tubular sliding sleeve l2. This area of radioactive material may be in the form ci a continuous band corresponding to that of phosphor |99. A rack |3 tted to sleeve It coacts with pinion I4 so that when pinion ifi is turned in one direction or the other the sleeve l2 will slide within the eye-piece tube IDI. As shown in Fig. 5, one extreme position of sleeve i2 results in a substantially complete overlapping of areas |09 and I D, whereas when the sleeve 2 is moved to the other extreme position, as shown in Fig. '2, the areas |09 and ||0 do not overlap at all. By this means the illumination of the reticle can be adjusted from maximum to substantially zero illumination, and likewise permits adjustment to all intermediate degrees of intensity of illumination. Two advantages of the embodiment of Figs. 5-7 are that it permits a greater area of glowing phosphor to be used on Ya given area of the edge of a reticle and, therefore, a greater degree of illumination is possible, and that the illumination is evenly distributed over the entire area of the edge of the reticle. However, it has been found that for most purposes the degree oi illumination and the degree of its uniformity provided by the embodiment first described are suiicient.

Instead of moving the area of radioactive material by sliding sleeve l2 (Fig. 6) that material may be affixed to the inner surface of tube ltl, so as to overlap or overlie the phosphor area. Then, if the end of sleeve I2 is shaped to slide between the two areas, in one extreme position it will completely screen the activating radiations from the phosphor surface, and in the other eX- treme position will not screen any of the radiations. Intermediate positions will provide any other desired change in the amount of radiations Which impinge on the phosphor surface. Such an arrangement involving interposing between the phosphor and the radioactive material a screen opaque to the phosphor-activating radiations is described in my mentioned application Ser. No. 668,379.

What is claimed is:

l.. In an optical instrument, a reticle and illuminating means therefor, said means comprising, a strip of non-radioactive luminescent material positioned in light-transmitting relation-to said reticle, a separate strip of non-luminescent radioactive substance positioned to activate said material, and adjustable means for varying the quantity of activating radiations from said substance which impinges on said material, whereby to adjust the intensity of illumination of said reticle.

2. In an optical instrument, a reticle and illuminating means therefor, said means comprising, an area of non-radioactive luminescent material positioned in light-transmitting relation to said reticle, a separate area of non-luminescent radioactive substance positioned to activate said material, and adjustable means for varying the quantity of activating radiations from said substance which impinges on said material, whereby to adjust the intensity of illumination of' said reticle.

3. In an optical instrument, a reticle and illuminating means therefor, said means comprising, a coating cinch-radioactive luminescent material secured to at least a portion of the periphery of said reticle, a separate area of non-luminescent radioactive substance positioned to activate said material, and adjustable .means for varying the quantity of activating radiations from said substance which impinge on said material, whereby to adjust the intensity of illumination of said reticle.

el. In an optical instrument, a reticle and illuiinating means therefor, said means comprising a strip of non-radioactive luminescent material positioned in light-transmitting relation to said reticle, a separate strip of non-luminescent radioactive substance positioned to activate said material, and means for moving one of said strips relative to the other to change the effective spacing therebetween for varying the quantity of activating radiations from said substance which iinpinge on said material, whereby to adjust the intensity of illumination of said reticle.

5. In an optical instrument, a reticle and illuminating means therefor, said means comprising an area of non-radioactive luminescent material coated on a band of translucent material positioned on the periphery of said reticle, a member coated with a separate area of non-luminescent radioactive substance positioned to activate said material when said areas overlap, and means for varying the intensity of illumination of said reticle comprising means for adjusting the amount of overlap of said areas.

6. In an optical instrument, a reticle and means for controlling the intensity of illumination thereof, said means comprising an area of non-radioactive luminescent phosphor positioned adjacent the periphery of said reticle to illuminate the same, a movable member positioned concentric with said periphery, an area of non-luminescent radioactive material positioned on a surface of said member so as to activate the entire area of said phosphor when said areas coincide, and means for moving said member so that said areas do not coincide.

7. In an optical instrument, a reticle and means for controlling the intensity of illumination thereof, said means comprising, an area of non-radioactive luminescent phosphor positioned on the periphery of said reticle, a movable member concentric with and closely spaced from said periphery, an area of non-luminescent radioactive metallic foil positioned on the surface of said member adjacent said phosphor so as to activate the same when said areas coincide, and means for adjusting the extent of the areas coinciding.

8. In an optical instrument, a reticle and means `for. controlling the intensity of illumination thereof, said means comprising, a plurality of fixed areas of non-radioactive luminescent phosphor spaced around the periphery of said reticle, a rotatable member concentric with and closely spaced from said periphery, a corresponding number of areas of non-luminescent radioactive metallic foil spaced around the surface of said movable member adjacent said phosphor areas so as to activate the same when said iixed and movable areas coincide, and means for rotating said member between a position Where said areas coincide and a position Where said areas do not coincide.

9. In an optical instrument, a reticle and means for controlling the intensity of illumination thereof, said means comprising, a plurality of xed areas of non-radioactive luminescent phosphor spaced around the periphery of said reticle, a ring-shaped rotatable member concentric With and closely spaced from said periphery, a corresponding number of areas of non-luminescent radioactive material spaced around the surface of said movable member adjacent said phosphor areas so as to activate the same when said fixed and movable areas coincide, means for rotating said member from a rst position where said areas do not coincide to a second position where said areas coincide, and means operable to return said member to said first position automatically upon release at said second position.

CLARENCE W. WALLHAUSEN.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 828,511 Saegmuller Aug. 14, 1906 863,287 Kunz Aug. 13, 1907 1,302,353 Friedrich Apr. 29, 1919 1,436,226 Alschuler Nov. 21, 1922 1,529,643 Fenderl Mar. 10, 1925 2,171,571 Karnes Sept. 5, 1939 2,270,307 Karnes Jan. 20, 1942 2,399,061 Rosenblum Apr. 23, 1946 2,403,316 Wallhausen July 2, 1946 2,405,026 Feuer et al July 30, 1946 

